Plant-level intensity of energy and CO2 emissions for Portland cement in Guizhou of Southwest China 2019–2022

Low-carbon development of ordinary Portland cement industry is of great significance to China’s target “to peak carbon dioxide emissions before 2030 and to achieve carbon neutrality before 2060”. Neglecting the regional heterogeneity in China, few studies emphasized the status and developments of energy intensity and CO2 emissions of ordinary Portland cement industry in Guizhou of Southwest China. To bridge this knowledge gap, we present an annual intensity dataset of energy and CO2 emissions at plant-level for Guizhou’s ordinary Portland cement industry, which involves the details of clinker rotary kilns, yearly production of clinker and cement products, fuel consumption and electricity consumption, total CO2 emission of cement products, energy intensity indicators of clinker and cement products, utilization ratio of solid-waste in clinker and cement production, and CO2 emission factors of cement products. It is an important supplement and to existing energy intensity and CO2 emissions estimates at plant-level and provincial official emissions inventories that converges all regions of China.


Background & Summary
Ordinary Portland cement (OPC cement) is a crucial material for civil and building engineering and is widely used in making concrete, mortar, and other products 1 .More than 98% of the OPC cement plants in China introduced the new suspension preheating (NSP) process in the last ten years.In the NSP process, the raw meals proportioned by milled limestone and siliceous ores are heated in a rotary kiln to first thermal dissociate calcium carbonate in limestone to calcium oxide, and then the calcium oxide reacts with silicon ores to form alite and belite for the clinker, while the temperature in the rotary kiln is up to 1400 °C and usually fired with fossil fuels 2 .The intermediate product clinker would be further milled with gypsum and other mineral admixtures, accounting for about ~25.0%, in the grinding mills to yield the OPC cement 3 .
The OPC cement industry is one of the most energy-intensive industries and generates a large amount of CO 2 emissions, responding to about 7.0% of China's total energy consumption and about 15.0% of total CO 2 emissions without significant variation annually [4][5][6] .More specially, about 0.4962~1.0015ton 7 , of CO 2 emissions that both for decarboxylation-derived and energy-derived CO 2 emissions 8 , are emitted per ton of the OPC cement produced with differences in materials of clinker and cement products, type of chosen clinker kiln, and burned fuels of kilns 9 .Thus, increasing attention should be paid to the national OPC cement-related CO 2 emissions, while the national production of OPC cement is approximately 21.3 billion tons in 2022 and share 51.2% of global OPC cement production 10 , and the realization of low-carbon development of the OPC cement industry will be of great significance to China's target "to peak carbon dioxide emissions before 2030 and to achieve carbon neutrality before 2060" 11 .
Past studies estimate that there are three major approaches to mitigating CO 2 emissions in the OPC cement industry to promote green transition and sustainable development 2 .Firstly, energy efficiency measures, such as new large-scale dry kilns and waste heat power generation technology to recover energy and waste heat 12 , are not only the basic strategy to improve energy intensity to enhance sustainability but also to reduce CO 2 emissions.Secondly, alternative fuels, such as municipal domestic waste, biomass, and coal gangue, are used in the rotary kiln 13,14 , and alternative materials, such as fly ash, phosphogypsum, desulfurization gypsum, construction & demolition waste, and mineral slags & coal cinder 15,16 , are substituted to reduce dependency on clinker to upgrade energy intensity of cement and reduce CO 2 emissions effectively 17,18 that not only energy-derived but also decarboxylation-derived. Lastly, the planned numerous pilots and larger-scale demonstrations for carbon capture and storage (CCS) have significant potentiality 19,20 .
As a typical less-developed mountainous region and the important ecological barrier in the upper reaches of the Yangtze River and the Pearl River, Guizhou province, located in Southwest China (Fig. 1), faces common structural environmental problems and special problems of serious lagging of infrastructure for ecological environment protection.More specifically, Guizhou not only needs to speed up its development and consolidate its achievements in poverty alleviation but also faces the challenges of dwindling resources and a degrading environment.Guizhou has high levels of coal, phosphorite, bauxite, and manganese in its soil, and a large amount of fly ash, red mud, and phosphogypsum accumulated in the related industrial production process share about 2.3~2.8% of the national general industrial solid-wastes, which results in the serious environmental pollution in their substantial discharge and stockpiling.Guizhou has also been responsible for 4.0~5.0% of China's total OPC cement production in recent years 21 , which could utilize a considerable amount of that solid-waste to reduce the demands for fuels and raw materials.The benefit of utilization of solid-waste from its OPC cement plants has not yet been systematically assessed, owing to limited data 22,23 .
To support the development of an effective carbon peaking policy implemented by provincial and county authorities and realize the energy and environmental benefits, it is necessary to compile an accurate dataset of the CO 2 emissions from China's OPC cement production that attracts worldwide attention.However, most studies emphasized the developments and status of that developed provinces or cities over backward Guizhou and Yunnan, neglecting the regional heterogeneity in China [24][25][26] , which cannot support the precise implementation of their high-quality development targets 26 .Thus, to the bridge knowledge gap, not only for the discrepancies and uncertainties, in the data for the OPC cement of the developing regions at the provincial or plant-level, we present an annual intensity dataset of energy and CO 2 emissions at plant-level for the OPC cement production in Guizhou of Southwest China from 2019 to 2022.This dataset involves the details of clinker rotary kilns, yearly production of the clinker and OPC cement products, fuel consumption and electricity consumption, total CO 2 emissions of the OPC cement products, energy intensity indicators of the clinker and OPC cement products, utilization ratio of the solid-waste in clinker and cement production, and CO 2 emissions factors of the OPC cement products.It is also an important supplement and to existing energy intensity and CO 2 emissions estimates at plant-level and provincial official emissions inventories that converges all regions of China.

Boundary definition and overview of OPC cement plants in Guizhou. The Ministry of Industry
and Information Technology of China (MIIT) has achieved full coverage of thousands of the OPC cement plants through the industrial energy conservation inspections since 2016 (https://www.miit.gov.cn/jgsj/jns/wjfb/art/2020/art_9db88c4f2bfe45d1adc651130bf3c541.html).From 2017, most municipal supervisory authorities of nine cities in Guizhou independently conducted the work of the industrial energy conservation inspections, including but not limited to cement plants, iron-steel plants, non-ferrous metallurgy plants, and thermal power plants.Although national The spatial boundary of this dataset covers the whole territory of Guizhou province, including Anshun City, Bijie City, Guiyang City, Liupanshui City, Qiannan City, Qiandongnan City, Qianxinan City, Tongren City, and Zunyi City.There are 74, 76, 75, and 75 OPC cement plants covering nearly 84, 86, 85, and 85 clinker rotary kilns all produced by the NSP process distributed steadily in the above nine regions in Guizhou province from 2019, respectively.Several plants have two or three clinker rotary kilns.There is a significant spatial discrepancy in capacity and quantity of clinker rotary kilns.Nearly half of the total capacity of clinker rotary kilns is still provided by outdated equipment whose production capacity less than 4000 t/d in clinker calcination.Figure 2 shows the city-level distributions of different clinker rotary kilns for the OPC cement plants from 2019.
Data collection and management.The primary yearly plant-level data from 2019 are mainly investigated and obtained from the special supervision for tiered pricing of electricity of cement plant, regarded as an indispensable part of the national industrial energy conservation inspections.The collected primary data includes the various fuel consumption, heat-value and carbon content of the fuel consumption, total production of clinker and OPC cement, electricity consumption, electricity supply of waste heat recovery unit, shares of calcium oxide and magnesium oxide in the clinker product, and details of utilized solid-waste.The energy intensity, CO 2 emissions or emissions factors, and utilization ratio of solid-waste, regarded as secondary data, are generally calculated from the primary data followed by the national standard of The Norm of Energy Consumption per Unit Product of Cement at https://std.samr.gov.cn/gb/search/gbDetailed?id=E116673EA6DAA3B7E05397BE0A0AC6BF, and 2006 IPCC Guidelines for National Greenhouse Gas Inventories at https://www.ipcc-nggip.iges.or.jp/public/2019rf/ index.html.The entire processing work of the present dataset is described in Fig. 3.
The relative uncertainties of those primary data are very low, considered to be or less than 1.0%, while those data were collected from openly available data of the OPC cement plants.The error propagation methods 27,28 , an alternative faster and more reliable than the Monte Carlo method within the same indicators, are used to calculate the relative uncertainties of the secondary data.
Energy intensity and CO 2 emissions for OPC cement product.According to the national standard of The Norm of Energy Consumption per Unit Product of Cement, the assessment the energy intensity indicators of the OPC cement products is estimated in Table 1.
The CO 2 emissions in the OPC cement plants mainly come from the decarboxylation of calcium carbonate and magnesium carbonate in the raw materials for cement products, fuel combustion, and external electricity consumption.According to 2006 IPCC Guidelines for National Greenhouse Gas Inventories, the assessment of CO 2 emissions of the OPC cement products is shown in Table 2.

Data Records
There are seven excel files in our dataset.The seven excel involve the details of clinker rotary kilns, yearly production of the clinker and OPC cement products, fuel consumption and electricity consumption, total CO 2 emissions of the OPC cement products, energy intensity indicators of the clinker and OPC cement products, utilization ratio of solid-waste in clinker and cement production, and CO 2 emissions factors of the OPC cement products (Table 3).The entire database has been uploaded and publicly available at the Figshare repository 29 and is available for download in excel format, and this dataset will be continuing to be updated annually.

technical Validation
Comparison of energy intensity with national standard.We compared our energy intensity results with estimates in The Norm of Energy Consumption per Unit Product of Cement to validate the energy intensity data given in this dataset, which is firstly shown in Fig. 4.There is a decreasing trend in fuel intensity of clinker, electricity intensity of clinker, energy intensity of clinker, electricity intensity of cement, and energy intensity of cement from 2019 to 2022.The plant-level estimates for the energy intensity of cement in Guizhou lie in the middle range, while the annual average energy intensity indicators are better than the advanced-level values for that in the national standard of GB 16780.The utilization of solid-waste is also beneficial for the energy intensity of cement that demonstrated negative correlations with utilization ratio of solid-waste in cement production from 2019 to 2022, as shown in Fig. 5.  Comparison of CO 2 emissions factor with existing references.Only a few references have provided provincial-level CO 2 emissions factors for Guizhou's cement industry.The decarboxylation-derived CO 2 emissions factor of cement products in Guizhou is usually estimated to be 0.4050 ton CO 2 /ton 30 or 0.5283 ton CO 2 / ton 4 , while that factor of the national level is estimated to be 0.5197 ton CO 2 /ton 31 .We plotted the plant-level CO 2 emissions factors of cement in Guizhou from 2019 to 2022 in Fig. 6.We can find that the decarboxylation-derived CO 2 emissions factor of cement products in this work is estimated to be (0.4567 ± 0.0641) ton CO 2 /ton in 2019, (0.4759 ± 0.0605) ton CO 2 /ton in 2020, (0.5046 ± 0.0612) ton CO 2 /ton in 2021, and (0.4589 ± 0.0482) ton CO 2 / ton in 2022, respectively.The results of decarboxylation-derived CO 2 emission factor can reflect the differences in the cement manufacturing process and kilns at the plant-level.The energy-derived CO 2 emissions factor of cement products is closely related to its energy intensity.Since nearly half of the total capacity of clinker rotary kilns in Guizhou is provided by outdated equipment, the energy-derived CO 2 emissions factor of cement products is higher than that of the national value 32 , which is been (0.2372 ± 0.0093) ton CO 2 /ton in 2019, (0.2694 ± 0.0235) ton CO 2 /ton in 2020, (0.2635 ± 0.0224) ton CO 2 / ton in 2021, and (0.2420 ± 0.0152) ton CO 2 /ton in 2022, respectively.
Limitations of Guizhou's plant-level intensity of energy and CO 2 emissions dataset.Although great efforts were made to guarantee the reliability of this dataset, the potential uncertainties in the data collection process were still unavoidable, mainly due to those specific time periods of the national industrial energy conservation inspections.Meanwhile, variations in fuel intensity and fuel-derived CO 2 emissions are inevitable, which applying the annual average heat value of coal in various plants.And the impact of the transfer of clinker and cement between different plants or different cities are not considered in this work.These shortcomings should be considered by users.

Usage Note
Although the dataset version in this manuscript relates to data collected from 2019 to 2022, the dataset of plant-level intensity of energy and CO 2 emissions for Portland cement in Guizhou will be updated in every October or November, while the results of the national industrial energy conservation inspections released by DIIT of Guizhou.This dataset is openly accessible to the public.This dataset is an important supplement and to existing energy intensity and CO 2 emissions estimates at plant-level and provincial official emissions inventories that converges all regions of China.Provincial and  county authorities can assess the impact of the production capacity and equipment in different cement plants on energy consumption and CO 2 emissions by this dataset, which helps to implement the development of an effective carbon peaking policy and to realize the energy and benefits.Managers and technicians can analyze this data to identify the superiority or inferiority in energy intensity and CO 2 emissions and make informed decisions regarding energy consumption and waste utilization.This dataset is openly accessible to the public.

Fig. 1
Fig. 1 Location and administrative area of Guizhou province in Southwest China.

Fig. 2
Fig. 2 Details of city-level clinker rotary kilns for OPC cement plants in Guizhou from 2019 to 2022.

Fig. 3
Fig. 3 Flowchart of entire processing work of this dataset.

Fig. 4
Fig. 4 Comparison of energy intensity indicators: (a) fuel intensity of clinker, (b) electricity intensity of clinker, (c) energy intensity of clinker, (d) electricity intensity of cement, and (e) energy intensity of cement at plantlevel in Guizhou from 2019 to 2022.

Fig. 5
Fig. 5 Benefit of utilization of solid-waste to energy intensity of cement at plant-level from 2019 to 2022.

Data Sources or calculation Relative uncertainty
Fuel consumption of clinker: m iFiled investigation 1.0%Heat-value of fuel:Q i Filed investigation 0.5%Heat-value of coal equivalent: Q ce 29307.6 kJ/kg Total production of clinker:P cl cl = ∑(m i × Q i )/(Q ce × P cl ) − 0.1229 × E re /P cl 2.1% Electricity intensity of clinker: EE cl EE cl = E cl /P cl 1.1% Energy intensity of clinker: EI cl EI cl = EF cl + 0.1229 × EE cl 2.3% Clinker consumption in grinding process: P cl-in cl = η × EI cl + F ce /P ce + 0.1229 × EE ce 3.6%

Table 1 .
Assessment of energy intensity indicators of OPC cement product.

Table 2 .
Assessment of CO 2 emissions of OPC cement products.

Table 3 .
Overview of seven excel files in present dataset.